The ai.Coach interface gains a grounding parameter carrying standing
context about the user (the knowledge port). buildPrompt injects an
"About the user" block only when grounding is non-empty, so an empty
grounding produces a byte-for-byte unchanged prompt. Drift judge and
nudge are untouched.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Addresses code-review follow-ups: codex now returns a specific error when
its -o file is empty rather than degrading to ErrEmptyResponse downstream;
CLI errors omit a dangling stderr suffix when stderr is empty.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
felixm